Sunroof motor running hot

[pmansson]

I have a spare one which I attached to a battery. It wasn´t the actual electric motor that got hot, but the 7" black plastic/rubber tubing around the wire (going to the gearbox).
And it got hot after just a few seconds of trying the engine....
What might be the issue here?

 

[61porsche]

Check the fuse box terminals, switch, wires, and motor for a voltage drop. Something is causing resistance which equals heat.

It's probable that the sunroof is wired with a series with other devices like windows, etc. If your switch is the mercedes type with the pins, clean it well.

 

[johanaxelson]

would seem to be a shortcircuit somewhere or if the motor is not running well i.e. has extra resistance when spinning it will draw more amps which will heat up the cables

if you open the motor to access the terminals you can measure and see what the issue is

 

[pmansson]

Thanks sofar, but in fact this is a spare motor. I´ve had it in my parts dept.
I just attached the wires to the battery poles and wanted to check if it worked.
Just as I do with the window motors.

 

[JhwShark]

Maybe the lubricant inside the motor is probably old, slowing the motor making it work harder and drawing more current.

Jon

 

[Arde]

You don't say if the motor does move, if it is stuck you will get a very high current and heat the wires.

 

[61porsche]

elec. motor overhaul

I haven't seen much documentation on repairing window motors and thought this might help someone here. ( Please disregard the regulator parts as it's a newer type with cables but as far as I know about electric motors the basics are the same.)
http://www.thesamba.com/vw/forum/viewtopic.php?t=406728

 

[pmansson]

The engine works fine, save for the heat in the cable going to the gearbox.
There is no grease or oil in the motor (perhaps a dab at the very bottom of the axle against the casing).
I suspect old grease in the gearbox. I will open it and check. If the old grease acts like a brake, I can understand the heating around the wire, inside the plastic cover.

I was servicing window motor gearboxes the other day, and only a few had very dry and hard grease. Most seemed OK, though I chose to remove the old, clean and fill with fresh grease.

I still cannot understand why BMW changed from the very fast sardine engines with separate gearboxes, to the later integrated ones. The difference in speed of windows going up and down is remarkable. Twice as fast on the old ones (providing the window channels, gearboxes, motor etc are in good shape.
The sad thing is that the early ones require the early doors, in order to mount them.